1. Field of the Invention
The present invention relates generally to packaging semiconductor devices for mass manufacture of electronic devices and, in particular, to packaging semiconductor devices using tape and reel packaging. Still more particularly, the present invention relates to machine vision and automatic inspection of markings on semiconductor devices in a tape and reel inspection system.
2. Description of the Related Art
Manufacture of electronic devices involves a good amount of automation. Circuit boards move along an assembly line, a robotic mechanism places the chips onto the boards, and the chips are attached to the circuit boards by passing the circuit boards over a pool of hot solder. As the solder cools, it bonds with the metal on the circuit board and the pins of the chips.
Due to the speed of the manufacturing process, manufacturers must provide a large number of chips to the automated equipment. For example, a graphics card may have several memory chips, each having the same size and number of pins. After chips are fabricated, they may be placed in several different containers, such as tubes or trays.
Another type of container is a tape and reel. Often, semiconductor devices, or chips, are placed into a carrier tape, which is a strip of plastic with pockets—each chip is placed into a pocket. As the carrier tape is wound onto a reel, a cover tape is sealed over the carrier tape. A reel may hold as many as 5000 chips, or possibly more. A reel may then be provided to automated manufacturing equipment, which then takes the chips from the tape and places them onto circuit boards.
It is important that all of the chips on a reel are, in fact, the same device. However, the possibility of mixing devices is significant. Many vastly different devices have the same die size and number of pins. A human operator can easily confuse two different chips. Also, each chip has a small area to mark a part number, and the part numbers may be very similar.
Tape and reeler inspection stations have been introduced to inspect the markings on chips as they are placed into the carrier tape. Tape and reeler inspection stations have machine vision systems, which use image pattern matching to ensure that every chip on a reel is the correct device. A human operator trains the system. Thus, tape and reeler inspection stations are susceptible to human error.